A liquid or powder dispenser device, in particular for dispensing fluids in the fields of pharmaceuticals, cosmetics, perfumes or the like, generally comprises a fluid reservoir, a dispensing member, such as a pump, for dispensing the fluid contained in the reservoir, and a dispensing head incorporating a dispensing orifice. An actuating system is generally also provided for actuating said pump. A problem that can arise with liquid or powder dispenser devices of this type relates to the period of time that elapses between the end of the device being assembled, and the occasion on which the user actually uses it. During that time lapse, it is necessary to prevent the dispensing orifice from becoming clogged or soiled, and to prevent the device from being actuated accidentally. Those problems are generally solved by providing a removable cap on the dispensing head, and a system for locking the device, which system prevents any accidental actuation of the device. For example, that may be achieved by means of a break-off strip or by means of a latch element to be moved out of the way prior to use. Although such systems are effective, they suffer from some drawbacks. The removable cap might be lost when it is removed from the dispensing head, so that the problem of the dispensing orifice becoming clogged can then arise after the first occasion on which the device is used, e.g. when the dispenser device is to be carried about in a handbag or the like. Similarly, safety systems for preventing the device from being actuated accidentally while it is being stored or carried can be complex and therefore costly to make, and they are not always entirely reliable.